\begin{tikzpicture}[scale=4]
\draw[style=dashed] (-1,0) node[above right] {$1$} node[below right] {$2$} -- (1,0);
\draw (-.8,-.4) -- (-.8,.4) node[below right]{$C$};
\draw (.8,.4) -- (.8,-.4);
\draw (-.8,-.4) -- (0,-.4);
\draw[<-] (0,-.4) node[below] {$\ud\ve l_1$} -- (.8,-.4);
\draw[->] (-.8,.4) -- (0,.4) node[above] {$\ud\ve l_2$};
\draw (0,.4) -- (.8,.4);
\end{tikzpicture}%
